1. Field of the Invention
The present invention relates generally to a plasma ignition system having a plasma ignition plug within each combustion chamber of an internal combustion engine, and more particularly to a plasma ignition system which does not require a mechanical distributor for applying a plasma ignition energy sequencially to one of a plurality of engine cylinders.
2. Description of the Prior Art
A conventional plasma ignition system comprises a DC power supply such as a vehicle battery, an ignition coil having a primary winding and a secondary winding, an interrupter connected to the ignition coil which opens and closes in synchronization with engine revolutions and a plurality of plasma ignition plugs, each mounted in a cylinder. The conventional system further utilizes a distributor having a drive shaft with a breaker cam and an advance mechanism. A breaker plate is provided with contact points, a capacitor for absorbing an arc generated as any one of the contacts is reopened, and a rotor, a drive shaft attached to the rotor driven by the engine camshaft through spiral gears, rotating at one-half crankshaft speed. The contact points open or close according to the rotation of the drive shaft and breaker cam, and the breaker cam rotates at half the crankshaft speed. The contact points, thus, close and open once for each cylinder with every breaker-cam rotation. Further, there is provided a first diode connected to the secondary winding of the ignition coil and to the rotor of the distributor; a second diode, connected to the rotor of the distributor; a current suppressing coil connected to the cathode terminal of the second diode; a voltage booster, connected to the plus polarity of the DC power supply; and a capacitor, connected to the output terminal of the voltage booster and to the coil.
In the conventional plasma ignition system described above, immediately after the interrupter opens, the secondary winding of the ignition coil provides a high-voltage surge for the rotor of the distributor via the first diode so that the insulation resistance between the central electrode and ground electrode of one of the plasma ignition plugs is reduced due to the dielectric breakdown within the discharge gap of the plasma ignition plug. At this time, an electric charge within the capacitor is discharged at the plasma ignition plug described above via the coil and second diode. Due to such high energy, a gas within the discharge gap is injected through the injection hole in the form of plasma gas to carry out the plasma ignition. However, there is a drawback in such conventional plasma ignition system, wherein the distributor described hereinafter is susceptible to suffer a trouble since the rotor is brought into a slidable contact with one of the contact points.